Abstract: Under the dual pressures of global climate change and coastal urbanization, China’s islands face a complex coordination dilemma between ecological conservation and economic development. In this study, the Evaluation Methods for Island Development Index and Evaluation Methods for Island Ecological Index were adopted to assess the development and ecological conditions of 59 islands in China. The coupling coordination degree model and the XGBoost algorithm were further applied to explore the interaction between the island development index (IDI) and the island ecological index (IEI), as well as their potential influencing factors. The results showed that the IDI of the selected islands ranges from 42.02 to 99.75, with an average of 69.39, indicating a favorable development status. The IDI exhibits a spatial differentiation pattern of “high in the south and low in the north”, with extreme values observed at Chongming Island (maximum 99.75) and Yuzhenzhou (minimum 42.02). The IEI of the selected islands ranges from 25.92 to 99.05, with an average of 61.50, indicating a moderate condition. Prominent polarization is observed between Weizhou Island in Guangxi (maximum 99.05) and Baisha Island in Zhejiang (minimum 25.92). The coupling coordination degree (D value) ranges from 0.248 to 0.952. Specifically, only 5.08% of the islands achieve excellent coordination, 20.34% reach good coordination, 67.80% are at the moderate-to-reluctant coordination level, and 6.78% are in a dysfunctional state. The spatial gradient of the coupling coordination degree is: East China Sea ＞ South China Sea ＞ Yellow Sea ＞ Bohai Sea. Vegetation area is the dominant driving factor with the highest feature importance for the IDI, IEI, and coupling coordination degree index. Island area and vegetation area make predominant positive contributions to the IDI. All impact factors positively affect the IEI at different levels except for the cultivated land area. Only the vegetation area has a positive effect on the coupling coordination degree index, while other factors show trivial fluctuations and no distinct directional effects. This study reveals the spatial differentiation and driving mechanisms of island development and ecology coordination in China, providing a scientific reference for the formulation of differentiated island management and control policies.